Skulls Taken!
From Halopedia, the Halo wiki
Skulls Taken!
Skulls Taken! is an achievement in Halo: Combat Evolved Anniversary. It is awarded for claiming five out of the ten campaign skulls. It is worth 25 Gamerpoints.[1]
It is represented by two human skulls on top of a white five-pointed star.
Trivia
The name of the achievement is mix direct quote of the Announcer in the Halo: Reach multiplayer Headhunter gametype when the player picks up a skull.
Sources